Nasal mask



FIG. 1 is a perspective view of a nasal mask showing our new design;

FIG. 2 is a rear view thereof;

FIG. 3 is a right side view thereof;

FIG. 4 is a cross-sectional view thereof, taken in the direction of line 4-4 of FIG. 3;

FIG. 5 is a rear view thereof; and,

FIG. 6 is a cross-sectional view thereof, taken in the direction of line 6-6 of FIG. 5.

The broken lines in the drawings illustrate portions of the nasal mask that form no part of the claimed design. 

CLAIM The ornamental design for a nasal mask, as shown and described. 